The use of physical unclonable functions (PUF) for authentication is known from DE 10 2010 038703 B3 and DE 10 2010 041447 A1, for example. Patent applications DE 10 2014 208975 A1 and DE 10 2014 209042 A1, not previously published, describe methods for secured communication in a distributed system on the basis of channel properties of the connected units. The latter methods belong to approaches, having the keyword “physical layer security,” which are being investigated and developed, and with the aid of which in particular keys for symmetrical methods may be automatically generated based on physical properties of the transmission channels between the involved nodes. In the process, use is made of the reciprocity and the inherent randomness of these transmission channels.